Urban road transportation causes se

Urban road transportation causes several major negative externalities. First, the costs of greenhouse
gas emissions from motorized private and public vehicles are borne globally. Second,
other air pollutants and noise from urban road transportation affect road users and others
locally. Third, while the costs of congestion (time delays and extra fuel consumption), accidents,
and infrastructure damage are largely borne by motorists collectively, there is still an externality
because individual motorists increase these costs for other motorists. Because of these externalities,
motorists do not bear the full social marginal costs of driving and they drive too much.
Urban road transportation causes several other externalities as well, including water pollution,
vibrations, and visual intrusion. Roads also create a barrier to bicyclists and pedestrians.
Moreover, when parking is underpriced, the time spent searching for parking, excessive use of
land for parking, the contribution to the urban heat island effect, and problems of drainage can
be significantinurbanareas (Shoup2005). Inaddition,fuelconsumptioncanimposecostsat the
national level due to monopsony power in the world oil market and energy insecurity, although
by most estimates the average costs are small (Bickel et al. 2006; Delucchi and McCubbin 2009).
Many policy instruments can be used to control road transportation externalities, but all have
their limitations. In the United States, vehicle emissions standards and ceilings on regional air
quality have helped reduce emissions per vehicle kilometer. Regulating vehicle safety, building